No abstract

The tieirral ~i i e c l i a~i i~~i i~ of limb coorditiofioti were itir-estigated by testing callosototriy patierits atid riorriial cotitrol srrhjccts o t i hitiiatirral tiiovemetits. Nortiid siibjects prodirced deviations iti the trrrjeitories wiieti spatial detricitidsfr,r the two hatids were different, despite tetiipornl syticlirotiy iti the otiset of hitriatiuril trioveltietits. Calhsototriy pritietits did t i d prodirce spntid deviutiotis, ciltlioiigli their liarids tiimed with tiorriiul tenipord syriclirotiy. Noritid sirhjects hirt riot ccillosototiiy pcitietits cxliibited Irirge iticrenses iti phitiitig cirid execiition time for ttiovettietits with differetit spntinl rleriioridsj?)r the two limds relative to triovetrierits with idetitictil spotid denicinds f.r the two hnwds. This tieiirril dissocintioti indicciies that spciticil ititerferetice in tnovemerits resirlts frotit ccillosal cotiticetioris, dierecis tetriporcil sytichrony in triovetiietit otiset does riot rely oti the corpirs callosirtii.

No abstract

When the left and right hands produce 2 different rhythms simultaneously, coordination of the hands is difficult unless the rhythms can be integrated into a unified temporal pattern. In the present study, the authors investigated whether a similar account can be applied to the spatial domain. Participants (N = 8) produced a movement trajectory of semicircular form in single-limb and bimanual conditions. In the bimanual tasks, 1 limb moved above the other in the frontal plane. Bimanual unified tasks were constructed so that the spatial paths to be produced by the 2 limbs could be easily conceptualized as parts of a unified circle pattern. Bimanual distinct tasks availed a less obvious spatial pattern that would unify the 2 tasks, despite similar demands placed on the coordination dynamics in the 2 cases (e.g., the phase relations). The authors conclude that a dual task becomes a single task, and interlimb interference is reduced, when the spatial patterns produced by the 2 hands form a geometric arrangement that can be conceptualized as a unified representation.

The effects of sensory signal characteristics on the duration discrimination of intermodal intervals was investigated in three experiments. Temporal intervals were marked by either the successive presentation of a visual then auditory signal (VA), or by the successive presentation of an auditory then visual signal (AV). The results indicated that (1) VA intervals are generally easier to discriminate than are AV intervals, but this effect depends on the range of duration studied; (2) AV intervals are perceived as longer than VA intervals for durations ranging from 250 to 750 msec; (3) the intensity of the visual markers for both AV and VA intervals does not affect the discrimination; and (4) the perceived duration of an intermodal interval is influenced by the length of the first and second markers. The results are mainly interpreted in terms of (1) a sensory trace left by visual and auditory signals and (2) the detection of these signals.